#ifndef STAN_MATH_PRIM_SCAL_FUN_BESSEL_SECOND_KIND_HPP
#define STAN_MATH_PRIM_SCAL_FUN_BESSEL_SECOND_KIND_HPP

#include <boost/math/special_functions/bessel.hpp>

namespace stan {
  namespace math {

    /**
     *
       \f[
       \mbox{bessel\_second\_kind}(v, x) =
       \begin{cases}
         \textrm{error} & \mbox{if } x \leq 0 \\
         Y_v(x) & \mbox{if } x > 0 \\[6pt]
         \textrm{NaN} & \mbox{if } x = \textrm{NaN}
       \end{cases}
       \f]

       \f[
       \frac{\partial\, \mbox{bessel\_second\_kind}(v, x)}{\partial x} =
       \begin{cases}
         \textrm{error} & \mbox{if } x \leq 0 \\
         \frac{\partial\, Y_v(x)}{\partial x} & \mbox{if } x > 0 \\[6pt]
         \textrm{NaN} & \mbox{if } x = \textrm{NaN}
       \end{cases}
       \f]

       \f[
       Y_v(x)=\frac{J_v(x)\cos(v\pi)-J_{-v}(x)}{\sin(v\pi)}
       \f]

       \f[
       \frac{\partial \, Y_v(x)}{\partial x} = \frac{v}{x}Y_v(x)-Y_{v+1}(x)
       \f]
     *
     */
    template <typename T2>
    inline T2
    bessel_second_kind(const int v, const T2 z) {
      return boost::math::cyl_neumann(v, z);
    }

  }
}

#endif
